1. Field of the Invention
The present invention relates to the field of semiconductor manufacturing and more particularly to a method of patterning a thin film.
2. Discussion of Related Art
Patterned thin films are used in many applications in the fabrication of semiconductor integrated circuits, micro-machines, and micro electromechanical systems (MEMS) devices. In order to pattern a thin film to the smallest photolithographic feature dimensions possible (e.g., critical dimensions) hard mask processes are typically used because photoresist mass can erode during the etching of the film and thereby create a profile in the film different than desired. A conventional hard mask patterning process is illustrated in FIGS. 1A-1D. First, a film to be patterned 104 is formed on a substrate 102. A hard mask layer 106 is then formed on the film to be patterned 104. A photoresist film is then formed on the hard mask material 106 and patterned into photoresist mask 108 having the feature patterned desired to be transferred into the thin film. A photoresist mask 108 is then formed on the hard mask layer 106. Next, as shown in FIG. 1B, the hard mask layer 106 is etched in alignment with the photoresist mask 108 to form a hard mask 110. Next, as shown in FIG. 1C, the photoresist layer can be removed and the film 104 etched in alignment with the hard mask 110 to form a patterned feature 112. Patterned feature 112, therefore, has the pattern originally formed in photoresist layer 108 and then transferred into hard mask 110. Next, as show in FIG. 1D, the hard mask 110 is removed from the patterned feature 112. The result is a patterned feature 112 formed in the film 104 having a feature shape and structure similar to that formed in photoresist layer 108. Unfortunately, the process used to removed the hard mask 110 can cause etching or pitting of the sidewalls of the structure 112 thereby altering the shape of the desired patterned feature.